Blade guard with dust collection

ABSTRACT

Blade guards for power tools such as table saws are disclosed. The blade guard may include a shroud that pivots up and down to allow a workpiece to move past the guard, a dust collection channel, and a pivot joint which maintains the dust collection channel in an operable condition as the shroud pivots up or down. The guard may also include a wood stop and anti-kickback pawls. The blade guard may be part of a dust collection system and may be connected to a vacuum system by a conduit such as a flexible hose.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority from the followingU.S. Provisional Patent Application, the disclosure of which is hereinincorporated by reference: Ser. No. 61/336,927, filed Jan. 27, 2010.

TECHNICAL FIELD

The present specification describes blade guards for power tools such astable saws. More specifically, the specification relates to blade guardswith dust collections systems, splitters, and anti-kickback devices.

BACKGROUND

A table saw is a power tool used to cut a workpiece to a desired size orshape. A table saw includes a work surface or table and a circular bladeextending up through the table. A person uses a table saw by holding aworkpiece on the table and feeding it past the spinning blade to make acut. A fair amount of sawdust is generated at the surface of a table sawas the blade cuts the workpiece and that dust can disperse into thesurrounding environment. Dust from wood and many other products commonlyprocessed in a workshop environment have been shown to pose a healthrisk to those who are exposed to the dust, especially if exposed to thedust on a regular basis. Thus, it is important to collect as much dustas possible at the time of cutting and thereby limit the dust thatescapes into the environment. The blade guards disclosed in thisspecification include systems to collect sawdust.

The disclosed blade guards also include a shroud to substantiallyenclose the blade and protect against contact with the blade, a splitteror spreader to support the shroud and to keep a workpiece from shiftingsideways and catching on the blade, an anti-kickback device such as aset of anti-kickback pawls configured to oppose a workpiece being thrownback toward a user, and/or a block to prevent a workpiece that is higherthan the top of the blade from contacting the spinning blade.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a table saw.

FIG. 2 shows the table saw of FIG. 1 equipped with a blade guard.

FIG. 3 shows a side view of the blade guard of FIG. 2 installed in thetable saw of FIG. 1 with the blade elevated and a piece of wood beingcut.

FIG. 4 shows a perspective view of the blade guard.

FIG. 5 shows the blade guard installed in the table saw of FIG. 1 withthe shroud and limit rod pivoted to an upright position.

FIG. 6 shows a left side view of the blade guard.

FIG. 7 shows a right side view of the blade guard.

FIG. 8 shows a perspective view of the blade guard.

FIG. 9 shows another perspective view of the blade guard.

FIG. 10 shows a front view of the blade guard.

FIG. 11 shows a back view of the blade guard.

FIG. 12 shows a top view of the blade guard.

FIG. 13 shows a bottom view of the blade guard.

FIG. 14 shows a side view of the blade guard with the shroud and limitrod pivoted to an upright position.

FIG. 15 shows a side view of the blade guard installed in the table sawof FIG. 1 with the blade elevated.

FIG. 16 shows an exploded view of the blade shroud of the blade guard.

FIG. 17 shows a perspective view of the upper shell of the blade shroud.

FIG. 18 shows a left side view of the upper shell of the blade shroud.

FIG. 19 shows a top view of the upper shell of the blade shroud.

FIG. 20 shows a bottom view of the upper shell of the blade shroud.

FIG. 21 shows a front view of the upper shell of the blade shroud.

FIG. 22 shows a rear view of the upper shell of the blade shroud.

FIG. 23 shows a perspective view of the bottom of the upper shell of theblade shroud.

FIG. 24 shows a side view of the blade guard installed in the table sawof FIG. 1 with the blade lowered.

FIG. 25 shows a perspective view of the right side extension of theblade shroud of FIG. 16.

FIG. 26 shows another perspective view of the right side extension.

FIG. 27 shows a side view of the right side extension.

FIG. 28 shows a top view of the right side extension.

FIG. 29 shows a bottom view of the right side extension.

FIG. 30 shows a front view of the right side extension.

FIG. 31 shows a rear view of the right side extension.

FIG. 32 shows a rear view of the left side extension of the bladeshroud.

FIG. 33 shows a top view of the left side extension.

FIG. 34 shows a side view of the left side extension.

FIG. 35 shows a side view of the blade guard of FIG. 4 with the leftpart of the blade shroud and dust port removed, and with arrowsindicating the flow of air and dust through the blade guard.

FIG. 36 shows a side view of the blade guard of FIG. 4 with the leftpart of the blade shroud and dust port removed and with arrowsindicating an undesirable airflow pattern in the blade guard.

FIG. 37 shows an exploded view of a splitter and dust port assembly usedin the blade guard.

FIG. 38 shows a left side view of the dust port of the blade guard.

FIG. 39 shows a right side view of the dust port of the blade guard.

FIG. 40 shows a top view of the dust port of the blade guard.

FIG. 41 shows a front view of the dust port of the blade guard.

FIG. 42 shows a rear view of the dust port of the blade guard.

FIG. 43 shows a perspective view of the dust port of the blade guard.

FIG. 44 shows another perspective view of the dust port of the bladeguard.

FIG. 45 shows another perspective view of the dust port of the bladeguard.

FIG. 46 shows another perspective view of the dust port of the bladeguard.

FIG. 47 shows another perspective view of the dust port of the bladeguard.

FIG. 48 shows the splitter and dust port assembly with the blade shroudremoved.

FIG. 49 shows a side view of the inside of the right dust port half witha spring installed.

FIG. 50 shows a perspective view of the inside of the right dust porthalf without a spring installed.

FIG. 51 shows a side view of the junction between the upper shell andthe dust port with the upper shell in a lowered position and the rightdust port half removed so that the position of the spring can be seen.

FIG. 52 shows a side view of the junction between the upper shell andthe dust port with the upper shell in an upright position and the rightdust port half removed so that the position of the spring can be seen.

FIG. 53 shows the blade guard with the blade shroud lowered and the leftdust port half removed so that the opening at the back of the pivotjoint can be seen.

FIG. 54 shows the blade guard with the blade shroud in an uprightposition and the left dust port half removed so that the closed surfaceof the pivot joint can be seen.

FIG. 55 shows a side view of the limit rod of the blade guard.

FIG. 56 shows the front of the wood stop on the limit rod of FIG. 55.

FIG. 57 shows a top view of the limit rod of FIG. 55.

FIG. 58 shows a perspective view of the limit rod of FIG. 55.

FIG. 59 shows a right anti-kickback pawl.

FIG. 60 shows another view of a right anti-kickback pawl.

FIG. 61 shows still another view of an anti-kickback pawl.

FIG. 62 shows a side view of an anti-kickback pawl.

FIG. 63 shows anti-kickback pawls angled to the left.

FIG. 64 shows a small anti-kickback pawl.

FIG. 65 shows another view of a small anti-kickback pawl.

FIG. 66 shows still another view of a small anti-kickback pawl.

FIG. 67 shows a side view of a small anti-kickback pawl.

FIG. 68 shows a spring for use with an anti-kickback pawl.

FIG. 69 shows another view of a spring.

FIG. 70 shows an anti-kickback pawl with a spring.

FIG. 71 shows a bushing for use with an anti-kickback pawl.

FIG. 72 shows another view of a bushing.

FIG. 73 shows still another view of a bushing.

FIG. 74 shows another spring for use with an anti-kickback pawl.

FIG. 75 shows another view of a spring.

FIG. 76 shows a small anti-kickback pawl with a spring.

FIG. 77 shows a blade guard with an extension on a dust port.

FIG. 78 shows another view of an extension on a dust port.

FIG. 79 shows a cross-sectional view of an extension for a dust port.

FIG. 80 shows another cross-sectional view of an extension for a dustport.

FIG. 81 shows a blade guard connected to a dust collection hose andconduit.

FIG. 82 is a schematic drawing of a blade guard connected to a vacuum.

FIG. 83 is another schematic drawing of a blade guard connected to avacuum system.

FIG. 84 is a schematic drawing of a vacuum system connected to a bladeguard and a table saw.

DETAILED DESCRIPTION

A table saw is shown at 10 in FIG. 1. Saw 10 includes a table 12 and acircular blade 14 that extends up through a slot 16 in a table insert 18that fits within an opening in the table. A piece of wood, or othermaterial to be cut, is placed on the table and pushed into contact withthe spinning blade to make a cut.

FIG. 2 shows the saw of FIG. 1 with a blade guard 20 installed. One ofthe purposes of the blade guard is to protect the user from coming intocontact with the spinning blade by providing a physical barrier to blockthe user's hand from moving into the blade. It is an accessory used forthrough-sawing, i.e., where the blade cuts through the top of aworkpiece, such as workpiece 22 shown in FIG. 3. Blade guard 20 is shownseparate from a saw in FIG. 4. The main body of the blade guard consistsof a blade shroud 24 that surrounds the blade and is pivotally attachedto a dust port 26. The dust port is rigidly bolted to a splitter 28 thatmounts in the saw and protrudes up through the table insert 18. When theblade guard is in use, the bottom of the blade shroud 24 rests on thetable insert or workpiece 22, as shown in FIGS. 2 and 3, and covers thetop and sides of the blade. When not in use, the blade shroud may bepivoted to an upright position to allow easy access to the blade, asshown in FIG. 5. FIGS. 6 through 14 show various views of the bladeguard.

As seen in FIGS. 15 and 16, blade shroud 24 is composed of an uppershell 30 and right and left side extensions, 32 and 34 respectively.These components are typically made of transparent polycarbonate toallow a user to see the blade through the shroud and side extensions.The upper shell covers the top and front of the blade while the sideextensions provide additional coverage along the sides of the bladebelow the upper shell.

FIG. 16 shows an exploded view of the blade shroud. The upper shell 30consists of two halves 36 and 38 that fit together with tongue andgroove mating 40 along their joining edges and which are fastenedtogether with seven small, self-threading screws 42. Each screw passesthrough a boss 44 in the right half 36, which catches the head of thescrew at the bottom of the boss, and then threads into a narrowernon-threaded boss 46 in the left half 38. Three of the screws are spreadout along the length of the top surface of the upper shell, three runalong the length of the blade guard shell at the middle of the uppershell and one is at the nose 48 of the blade guard. Nose 48 extends outfrom the upper shell in front of the blade as shown in FIG. 15. FIGS. 17through 23 show various views of the upper shell isolated from otherstructure. As seen in FIG. 17, the upper shell is wider at the nose andtappers inwards moving towards the rear to allow clearance for otherparts of the blade guard near the rear of the blade guard. The widernose helps prevent the blade guard from hitting the blade if bumped fromthe side. This is particularly important when the blade and blade guardare tilted at 45 degrees relative to the table because in that positionthe blade guard has a greater tendency to deflect inward or toward theblade. As shown in FIG. 18, a ridge 50 runs along the upper shell nearthe bottom edge and curls up the side of each upper shell half near therear to make the upper shell stronger.

Side extensions 32 and 34 are flat (or planar), generally rectangularshaped pieces attached to the upper shell in such a way that they arefree to pivot up and down individually. To allow the side extensions topivot, two self-threading screws 52, one for each side extension, attachthe front end of a side extension to the front end of an upper shellhalf near the nose. As shown in FIGS. 16, 27 and 34, each side extensionhas a circular raised region 54 toward the front end and on theoutward-facing side, and the circular region has a hole 56 in the centerabout which the side extension pivots. The circular raised region 54fits within a corresponding oval hole 58 in each upper shell half. Ascrew 52 passes through a polycarbonate finish washer 60, then throughthe hole 56 in the side extension and threads into a boss 62 (which inthe illustrated embodiment is continuous with raised region 54) thatextends inward from the inner side of the side extension, as shown inFIGS. 16, 26, 28 and 29. When the blade is lowered, the blade guardmoves down with the blade and the side extensions contact the table orworkpiece and pivot upward about screws 52, as shown by the position ofthe side extensions in FIG. 24. The side extensions fit within the sidewalls of the upper shell such that when the side extensions are pivotedupwards fully, a flange 64 along the bottom edge 66 of each sideextension runs along and underneath the bottom edges 68 of the uppershell, and the top edges 70 of the side extensions follow along and justbelow a contour 72 that projects outward along the middle of the outersurface of the upper shell. The upper shell is wider in the area wherethe side extensions reside so that they are kept away from the blade.When the blade is fully raised, the side extensions pivot downward undergravity so that the bottom edges 66 of the side extensions remainhorizontal on the surface of the table insert or workpiece, as shown inFIG. 3. The side extensions help cover the sides of the blade leftexposed as the back end of the upper shell rises.

FIGS. 25 through 34 show various views of the side extensions isolatedfrom other structure. As shown in FIGS. 27 and 34, the front end 74 ofeach side extension is shaped like a semicircle that is taller than therest of the side extension. These semicircular ends 74 extend radiallyoutward from the point about which the side extensions pivot in order torestrict the sideways movement of the side extensions so that they donot flex inward and contact the blade. The middle area of thesemi-circular ends between the outer edge and the outskirts of hole 56is recessed on the outward-facing side (i.e., the side which faces theinside wall of the upper shell). The recessed area 76 helps reducefriction as the side extensions pivot up and down. Each recessed area issurrounded by a border 78 that runs along the outside edge of thesemi-circular region and in front of hole 56 and gradually tapers intothe thickness of the side extension to create the recessed area, as seenin FIG. 25. There is an opening 80 in the border for one short segmentalong the upper rear of the semi-circular end. The opening 80 allowsdust that may accumulate in the recessed area to escape.

As shown in at least FIGS. 25 through 34, the tip 82 of a triangularlyshaped molded protrusion 84 at the upper, rear corner of each sideextension, is positioned to slide along the splitter when the sideextensions pivot up or down, thereby helping to keep the side extensionsfrom moving inward and contacting the blade. The triangle 84 ispositioned back far enough on each side extension so as not to hit theteeth of the blade. As shown in FIG. 28, the front and back of triangle84 have sloped surfaces 86 and 88 that meet at the tip 82. In addition,triangle 84 has surfaces 90 and 92 that slope down from the top and upfrom the bottom respectively and which meet the front and back slopedsurfaces 86 and 88 to form tip 82, as shown in FIGS. 30 and 31. Tip 82is not sharp but smooth and flattened. The sloped sides of the trianglesare shaped in such a way as to keep the triangles on each side extensionfrom catching on each other or on the splitter when the side extensionspass by each other or when they pass by the top of the splitter as theypivot up and down.

As mentioned earlier, a flange 64 lies along the bottom of each sideextension. The flange tapers outward from the front of the blade guardtowards the rear. The flange provides strength and also helps keep theside extension from bowing or flexing inward.

As a workpiece is moved towards the blade with the blade guard in place,the workpiece first encounters the nose 48 of the upper shell. The nose48 is shaped in such a way that the workpiece can easily slide under thenose and raise the blade shroud as it slides under. The nose of theblade guard includes a tip 94 and a surface 96 that slopes down from thetip toward the blade at an angle, as shown in FIGS. 15, 18 and 23, sothat as the workpiece contacts the sloped surface 96 it pushes the noseup as the workpiece moves towards the blade. The height of the nose isdetermined by the maximum height of a workpiece to be cut with the bladeguard installed. This, in turn, is determined by the maximum height ofthe blade. Given the height of the nose, the length of the nose is acompromise between keeping the nose short and creating a slope thatenables the workpiece to smoothly engage the nose and lift the guard.The less steep the slope, the longer the nose and the more smoothly theworkpiece engages the blade guard. Sloped surface 96 at the front of thenose curves to join a bottom surface 102 of the upper shell. With thisconfiguration, bottom surface 102 maintains contact with the top surfaceof the table insert or with the top surface of the workpiece as theupper shell pivots.

When the blade is fully lowered, or when the workpiece has a maximumthickness, the upper shell is pivoted such that the bottom edge 68 ofthe upper shell is nearly horizontal relative to the table or workpiece,and bottom surface 102 rests on the table or workpiece. Bottom surface102 continues for a short distance and then ends, leaving the bottom ofthe upper shell open, as shown at 104 in FIG. 23. The bottom edges 68 ofthe sides of the upper shell continue towards the rear of the bladeguard for a short distance after bottom surface 102 ends, as shown at106 in FIG. 23, and then each side curves upward, as shown at 108 inFIGS. 18, 23 and 24, just enough to make room for the flanges 64 thatrun along the bottom edges of each side extension.

As shown in FIGS. 17 and 18, the nose of the upper shell includescutouts 98 on the side and top areas to allow the user to see the blademore clearly, especially as the workpiece contacts the blade. Thecutouts also make the nose of the guard lighter and thus easier to lift,which is important when the blade is tilted at forty-five degrees andthe wood approaches the blade at a forty-five degree miter gauge angle.A heavy nose in this situation could possibly cause the workpiece tobind against the blade guard. The borders 100 of the cutouts are formedby bending the material of the upper shell inward along the edges of thecutouts creating a webbed framework which adds strength to the nose. Thecutouts also provide finger slots for lifting the blade.

As a workpiece slides under the nose of the blade guard, the upper shellpivots around the point where it connects to the dustport. When aworkpiece slides under the nose of the blade guard and raises the uppershell, the back ends of the side extensions pivot downward under gravityto shield the sides of the blade. Oval hole 58 in the upper shell, shownin FIGS. 17 and 18, is slightly tilted forward to allow some verticalleeway for the pivot point of the side extension with regard to theupper shell. This enables the side extensions to remain horizontal andfully in contact with the surface of the workpiece as the upper shellrises. This leeway also gives the side extensions some freedom ofmovement to prevent a workpiece from stubbing against the front, bottomcorners 110 of each side extension as the workpiece is moved toward theblade (the bottom corners are labeled in FIGS. 25 and 27). Bottomcorners 110 allow clearance for the semicircular ends 74 of the sideextensions to fit within the upper shell. Also to prevent stubbing,corners 110 are rounded at a radius that allows a smooth transition. Theforward slanting front edges 112 of corners 110, located underneath andadjacent semicircular ends 74, abut edge 114 of the surface that wrapsunder the blade guard nose (edge 114 is labeled in FIG. 23) to limit thedownward pivoting of the side extensions.

When the blade tilts to the left, the blade guard also tilts to theleft. To keep both side extensions of the blade guard in contact withthe table insert or workpiece as much as possible, the bottom edge ofthe left half of upper shell 38 is higher than the bottom edge of theright half. In other words, the left half of the upper shell graduallybecomes shorter moving to the rear than the right half 36, as can beseen at 116 and 118 in FIGS. 18 and 23. This provides clearance to allowthe blade guard to tilt to the left while minimizing any exposure of theblade on the right side. Correspondingly, the top edge of the left sideextension 34 is shorter vertically than the right side extension 32, ascan be seen by comparing FIGS. 27 and 34, to allow the left sideextension to pivot into the upper shell without bumping the top of theupper shell. This configuration provides better blade coverage when theblade is tilted to the left.

A dust port designed to accommodate a vacuum hose is sometimesincorporated into the blade guard to capture dust generated above thetable surface during cutting operations. A dust port might extend fromthe blade shroud surrounding the blade and a flexible dust collectionhose might be connected to the dust port. However, the weight and angleof the hose could cause the blade shroud to move out of position,possibly contacting or exposing the blade, because the blade shroud isfree to pivot and is not rigid. To solve this problem, the blade guarddescribed herein includes a dust port rigidly attached to the splitter,and a joint between the dust port and blade shroud which allows theshroud to pivot and dust in the blade guard to travel through the jointand into a vacuum or vacuum system.

Blade guard 20 is designed to channel dust generated above the tablesurface so that the dust can be collected and removed through a dustport 26 that is rigidly supported by splitter 28. As shown in FIGS. 16,35 and 36, the upper shell 30 includes a divider wall 120 which extendsinward from each upper shell half and mates in the middle with tongueand groove edges. The divider wall is positioned such that it runs alongand slightly over the top of the blade and splitter. The divider wallextends from the rear of the upper shell towards the nose, and ends justbefore the point where the side extensions are attached to the uppershell. The divider wall creates a dust channel 124, labeled in FIG. 35.The dust channel can be thought of as beginning below divider wall 120at the back of the blade and extending towards the nose at the front ofthe blade guard. The channel then wraps upward and turns back above thedividing wall and extends toward the splitter. FIG. 35 includes a dashedline 125 that illustrates how dust can move through the channel from therear of the blade toward the front, and then back toward the splitterand through dust port 26.

At the front of the blade guard, channel 124 curves up and back towardthe splitter by a bend 126, labeled in FIGS. 16 and 35. Surface 102 atthe bottom of the nose, in combination with a zero-clearance tableinsert 18, peels or scrapes from the blade the air that the blade putsinto motion and bend 126 redirects the air up into the dust channelabove the divider wall. With the blade at or near full height, the bladetends to move air down toward the table. In that case, experimentationhas shown that surface 102 is optimally positioned 10 mm or less fromthe forward edge of the blade. When the blade is just slightly above thetable, the blade directs air forward, into bend 126. The radius ofcurvature of bend 126 is chosen to create a cross-sectional areaoptimized to catch the air flow generated by the blade. Across-sectional area that is too small will constrict the airflow. Ifdividing wall 120 ends farther back from the nose, making thecross-sectional area within bend 126 larger, curls are created in theairflow pattern which carry or re-circulate dust back down and whichprevent or hinder dust from moving along the dust channel toward dustport 26. FIG. 36 shows a dashed arrow 132 which represents such acurling airflow pattern.

An important part of the design is the position of the end of thedividing wall relative to the center of the curvature of bend 126. Foroptimal air flow into and around the bend, the dividing wall ends at apoint below the center of curvature so that the air strikes the dividingwall at an angle that deflects the air and dust upward, around the bendand through channel 124. If the dividing wall ended at a point higher orequal to the vertical position to the center of curvature of bend 126,air could strike the dividing wall and be deflected downward toward thetable.

The dust channel above the dividing wall can be sized generally tomaintain the optimized cross-sectional area of bend 126 along itslength. Alternatively, the cross-sectional area may be varied to movethe air faster or slower in one or more parts with a correspondingvariation in airflow resistance. The channel may change shape over itslength. In the depicted embodiment, the cross-sectional area of the dustchannel at bend 126 is approximately 850 mm², it decreases toapproximately 400 mm² adjacent the pivot joint, and then returns toapproximately 850 mm² at the end of the dust outlet.

Below divider wall 120 the upper shell and side extensions closelysurround the blade, substantially trapping a volume of air which is thenpushed forward by the spinning blade. The side extensions play asignificant role in trapping the air because they cover the sides of theblades. A large percentage of the airflow through the dust channel wouldbe lost without the side extensions containing and directing theairflow. For air to flow through the blade guard, replacement air entersthe blade guard from the rear and up through the slot in thezero-clearance table insert near the splitter. When the blade is raised,the blade moves a larger volume of air that is trapped in the bladeguard and thus a larger volume of air flows into the channel. In thiscase, air enters at the rear of the blade guard below the dividing walland also through the gaps along the side of the blade between the upperblade guard shell and the side extensions and also through the slot inthe zero-clearance insert. When the blade is lowered, more air entersthe blade guard by coming up though the slot in the table insert, butthe side extensions inhibit air from entering the guard along the sideof the blade so the blade guard shell includes a cutout 134 at the backbelow the divider wall, as shown in FIG. 23, to allow whateveradditional air is needed to enter the guard and keep the dust movingalong the dust channel.

Dust channel 124 continues from the upper shell into dust port 26, asshown in FIG. 35. As shown in FIG. 37, the dust port is made of twohalves, a left half 136 and a right half 138, held together by fourscrews 140 and two bolts 264 and 266 that bolt the front, lower portionof the dust port to the splitter. Screws 140 pass through holes 142 inthe left dust port half 136 and then through corresponding holes in theright dust port half 138 where they are secured with nuts 146 which fitinto hexagonal shaped cavities 148, shown in FIG. 39, on the outside ofthe right dust port half 138 to keep the nuts from turning as the screwsare tightened. Bolts 264 and 266 are similarly secured by nuts 280 and312, respectively. Tongue and groove mating 150, positioned along theedges where the two halves of the dust port join together, help seal thedust channel within the dust port. Various views of dust port 26 areshown in FIGS. 38 through 47.

Dust channel 124 passes from the upper shell into the dust port througha specially designed pivot joint 152, labeled in FIGS. 8 and 14. Thepivot joint is designed to allow the blade shroud to pivot up and downwhile maintaining a sealed dust channel through the joint. The pivotjoint is formed by circular regions 154 (labeled in FIGS. 16-18) moldedinto the rear of each upper shell half of the blade shroud. As shown inFIG. 16, each circular region 154 has a flat, circular, vertical surface158 surrounded along the top, bottom and half-way down the back bysurfaces 160 that are perpendicular to the vertical surface and whichmate together with tongue and groove mating when the two upper shellhalves are put together. The tongue and groove edges help seal the dustchannel through the pivot joint. The lower, back portion of the circularregions 154 are left open so that when the two upper shell halves arejoined together, they form an opening 162 (labeled in FIGS. 23 and 53)to allow dust moving in the channel to pass through the opening 162 andinto dust port 26.

The two halves of dust port 26 include circular regions 156 that form adonut shaped region. Circular regions 156 in the dust port fit over thecircular regions 154 in the blade shroud to connect the blade shroud tothe dust port and to form the pivot joint. At the center of the pivotjoint is a pin 164 that runs through a hole 166 in one dust portcircular region, as shown in FIG. 48, and through holes 168 in thecircular regions in the upper shell halves, and then through a hole 166in the other dust port circular region. Pin 164 is held in place bye-clips 170 which fit into grooves 172 in the pin, one e-clip located ateach end of the pin on either side of the dust port. The upper shell,and thus the shroud, is able to pivot about pin 164. The dust channelwidens in pivot joint 152 to provide room for pin 164 while maintainingessentially the same cross sectional area as the rest of the dustchannel.

Ridges are formed on the outer surfaces of the upper shell circularregions 154 which serve as standoffs between the upper shell and thedust port. The ridges provide strength and keep the upper shell fromwobbling from side to side. As shown in FIGS. 17 and 51, a ridge 174 inthe form of a hollow cylinder projects perpendicularly out from themiddle of the circular region on the outside surface of each uppershell. Another slightly shorter ridge 176, in the shape of ahalf-cylinder, is concentric with ridge 174 but has a larger diameter.Four fairly evenly spaced spokes 178 extend radially outward from ridge174 along a slanted, forward and upper half portion of the ridge. Thespokes pass through ridge 176 with one spoke at each end of ridge 176,as shown in FIG. 51. The ends of the spokes taper down to the surface ofthe upper shell near the edge of the circular region. Except for thesmaller cylindrical ridge 174, a small gap is left between the outermostsurfaces of the ridges and the inner surfaces of the dust port; onlyridge 174 makes contact with the inner surface of the dust port in orderto reduce friction as the upper shell pivots. An additional set ofspoke-like ridges 192, shown in FIG. 38, are formed on the outside ofthe dust port donut-shaped regions 156 in order to strengthen the dustport and the pivot joint.

The blade shroud described above can pivot from a lowered position thatallows the side extensions to rest on the table surface to an uprightposition that allows access to the blade. When the blade shroud ispivoted to an upright position, a hump 180 on the top of the dust port(shown in FIGS. 51 and 52) contacts the upper shell to keep it frompivoting too far back. The hump is positioned and shaped so the bladeshroud can pivot up, past a vertical center, so that a user can raisethe blade shroud to access the blade and the shroud will stay in the upposition by the shroud resting against the hump. The shroud may includea curved surface to mate with the hump.

When the blade guard is taken out of the saw, the plastic boss aroundone of the screws 42 on the underside of the upper shell hits a dip 182along the top of the splitter (dip 182 is labeled in FIG. 14) whichkeeps the upper shell from rotating too far downward, which would makethe blade guard awkward to handle.

Dust port 26 includes two springs 184 located in the pivot joint, one ineach dust port half, as shown in FIGS. 48, 49, 51 and 52. The springspush against the blade shroud to lighten the load at the nose of theblade guard so that the blade shroud is easier to lift. The bottom ofeach spring fits within a groove 186 on the inside lower part of thepivot joint, as shown in FIG. 50. A rectangular enclosure 188 extendsoutward from the inside wall of the dust port and encloses the middleand lower portion of the spring on three sides to hold the spring inplace. The enclosure 188 is actually formed out of material from thedust port in the donut shaped regions 156 that is pushed inward leavingan opening on the side of the pivot joint where the spring can be seenfrom the outside, as shown in FIG. 38. The enclosure is formed this wayso that the whole dust port half can be made with one mold. The springis situated at a forward angle and when the blade shroud is in itshorizontal position, the top of the spring presses against a ridge 190in the upper shell of the blade shroud, as illustrated in FIG. 51. Whenthe blade shroud is raised, the spring is relaxed, as illustrated inFIG. 52. A small area of material is removed from each dust port half atthe bottom of the spring, as shown at 189 in FIG. 49, to allow dust thatmay fall onto the spring to escape so that it does not collect in theenclosure and interfere with the operation of the spring.

A blade guard as described above creates a powerful airflow thatredirects and forcefully blows dust out through outlet 194 in dust port26 (outlet 194 is labeled in FIG. 43). The dust leaving outlet 194 canbe left to collect in a pile, it can be collected by a bag attached tothe outlet, or better yet, it can be collected by a vacuum systemconnected to the outlet. Outlet 194 is shaped to accommodate the end ofa vacuum hose. The inside surfaces of the dust port are slightly taperedinward moving into the port to match the taper of many vacuum hoses.This allows the hose to connect to the port by a press-fit.

The design of the pivot joint 152 enables the dust channel to be closedwhen the table saw is not in use so that another tool hooked up to thesame vacuum system will not lose suction. Pivoting the blade shroud toits upright position rotates the opening at the back of the upper shelldownwards, thereby closing off the dust channel, as shown in FIG. 54.The bottom inside surface of the dust port slopes upward as itapproaches the pivot joint from the rear, as can be seen at 196 in FIG.51, and this helps seal the area between the blade shroud and the dustport at the bottom of opening 162 to help keep dust from escaping.

A dust port and pivot joint as described above allows a blade guard toinclude effective dust collection while still including a blade shroudthat is able to pivot up and down to allow a workpiece to approach theblade. The rigid support of the dust port and pivot joint prevents avacuum hose from moving the blade shroud out of position and alsoreduces the risk of the vacuum hose disconnecting as the blade guardmoves.

Blade guards equipped with a rigidly supported dust port and pivot jointmay also include a limit rod or material block to prevent a user fromfeeding a workpiece into the blade that is too tall or thick to movepast the rear portion of the blade guard. A workpiece that is too tallwill not be able to pass through the blade guard because it will bumpinto the splitter, anti-kickback pawls, or some other component of theblade guard as it moves past the blade. In that situation, the workpiecewill have to be pulled back towards the user to remove it from the bladeguard.

In order to prevent a piece of wood or workpiece that is taller than theheight of the blade from entering the blade guard described herein, alimit rod 198, shown in FIG. 4, extends out past the front of the bladeguard. The limit rod includes a wood stop 200 at its forward most end,and a workpiece that is too tall will hit the wood stop 200 and bestopped before it contacts the blade shroud.

FIGS. 55 through 58 show various views of the limit rod isolated fromother structure. As stated, the limit rod includes a wood stop 200 atits forward end. Wood stop 200 consists of a piece made of a light,rigid material, such as aluminum or plastic, generally triangular inshape and pointed downward with the tip clipped so that there is a flatsurface 202 along the bottom, as shown in FIG. 56. As shown In FIG. 14,the limit rod can be rotated up to an upright position. The flat surface202 along the bottom distributes a load over a larger area to minimizedamage that may occur if the limit rod is accidently bumped from anupright position so that it falls forward towards the table underfreefall.

In use, the left end 206 of the flat surface 202 stays near thecenterline of the blade as the blade tilts to the left so that the leftend 206 remains at the same height. The wood stop may be asymmetric ifcentered with respect to the blade, or symmetric if offset with respectto the blade. Either way, the left side 204 of the wood stop is angledat 45 degrees or more from the surface of the table (when flat surface202 is parallel to the table top) to prevent interference with the tablewhen the blade is tilted up to 45 degrees. The right side of the woodstop 208 may or may not be angled.

Wood or any other workpiece that is higher than the lowest point on thewood stop and which is being fed into the saw blade at an angle willtend to cause the wood stop to deflect as the wood encounters a slopedleft or right side, 204 or 208, of the wood stop if the side is smooth.Instead of stopping the wood, the wood stop will simply ride up the edgeof the wood. To prevent this, dimples or notches 210 are cut out alongthe left and right sides, 204 and 208, of the wood stop as shown in FIG.56. The notches are formed by small sections that slope inward whenmoving towards the bottom of the wood stop, as shown at 212, and thenabruptly change to slope outward along a very small segment 214. Whenthe wood encounters the wood stop at an angle, it slides along thelonger inwardly sloped section 212 of the notch 210 until it catches onthe small segment 214, at which point the wood is stopped. Puttingnotches along the left and right sides of the wood stop is only one wayto reduce the slickness of the side surfaces so that the wood is stoppedwhen it encounters the wood stop. Notches are not needed along thebottom, flat surface 202 even though this surface is at an angle whenthe blade is tilted. This is because in this orientation the limit rodis more rigid and resists moving upwards when the wood encounters theflat surface. However, notches could be added along the bottom surface,if desired.

Areas 216 may be cut out from the face of wood stop 200 to keep the woodstop lightweight and to facilitate manufacturing if the wood stop is anextruded part. The larger the cutouts and the larger the radii at thecorners of the cutouts, the easier it is to extrude the part. As shownin FIG. 56, cutout areas 216 are separated by ribs 218 extending fromthe top to the bottom of the wood stop. The ribs are positioned toprovide structural strength to the wood stop most particularly along theflat bottom section 202 that would take the impact if the limit rod wereto fall towards the table from an upright position. The ribs are aboutthe same width as the rest of the structure of the wood stop to helpwith material flow in the extrusion process and to keep cooling timesuniform in order to reduce warping.

Wood stop 200 has two holes 220 through its face, one at the top leftcorner and one at the top right corner, as shown in FIG. 56. Holes 220are for mounting the wood stop on the ends of two metal rods 222 whichpass through the holes. The holes are drilled through the wood stop at aslight angle so that the wood stop will be oriented generally verticalwhile the rods slope slightly downward as they extend towards the frontof the blade guard. The rods pass through the holes with the top half ofthe ends of the rods protruding out slightly farther through the frontof the wood stop since the rods are at an angle relative to the woodstop. The holes are made slightly smaller than the rods and a smallchamfer 224 at the end of each rod allows the rods to be forced into theholes in the wood stop. This stretches the material of the wood stop andcreates a press-fit that holds the rods in place. The rods and wood stopcould be joined in other alternative ways, such as with screws andadhesives or they could be welded.

Limit rod 198 is designed for use with a dust port as describedpreviously. Dust port 26 includes holes 228 positioned on the top of thedust port toward the rear, as shown in FIGS. 38 and 39. The ends of rods222 opposite the wood stop are bent at an angle near 90 degrees, asshown in FIG. 57. Bent ends 226 fit into holes 228 at the top of thedust port, on either side of the dust port, as shown in FIG. 4. Theinside surfaces of holes 228 taper outwards moving into the dust port toaccommodate a tolerance in the bend of the rods. The rods make contactwith the holes at a point near the entrance where the radius of the bendin the rod is nearly always the same as a result of the manufacturingprocess.

As shown in FIGS. 4 and 46, two fingers 230 extend up from the top ofthe dust port, one along the outside of each rod, to capture the rods sothat the ends of the rods do not fall out of holes 228. The fingers areformed by a sloped front surface 232 and a vertical back surface 234that are both perpendicular to a side surface 236 that spans the spacein between the inner edges of the front and back surfaces, as shown inat least FIGS. 38 and 47. The front and back surfaces meet at the toplike a triangle forming the fingers. A flat, horizontal surface 238intersects the front and back surfaces on each finger just above thedust port and stretches across the dust port between the two fingers, asshown in FIG. 48. Flat surface 238 provides a place upon which rods 222may rest. The area along the outside of the dust port between frontsurface 232 and back surface 234 is left empty to keep the thicknessesof the surfaces about the same. This minimizes warping distortions thatmay occur when areas of different thicknesses cool in the manufacturingof the molded plastic dust port.

FIG. 3 shows limit rod 198 in its locked position running generallyhorizontal alongside blade guard 20. To keep the rods stiff and thedeflection of the wood stop at a minimum, the limit rod is angledslightly downward moving towards the front of the blade guard and it iskept in position and some tension by snap-lock retaining grooves 240,best seen in FIG. 46, on either side of the dust port. As the limit rodis lowered from its upright position, it first encounters the slopedsurfaces 242 on three of the dust port structural ridges 192 that extendout from hole 166 at the center of the pivot joint to form part of thesnap-lock retaining grooves which hold the limit rod in place. Surfaces242 slope outwards moving down so that they move the two rods apart asthe rods are lowered. The surfaces 242 then end abruptly and the rodsfall into grooves 240 just below the end of the sloped surfaces to lockthe limit rod in place. The distance between the inner wall 246 of eachgroove 240 is wider than the distance that there would naturally bebetween the rods so that the rods are somewhat bowed outwardly when theysnap into place to create tension in the rods. Bowing the rods outwardalso provides clearance for other dust port features. The tension isfurther increased by the fingers 230 at the back of the dust port andwood stop 200 at the front of the rods which limit the distance betweenthe rods. Moving forward from the rear of the limit rod, the distancebetween the rods increases more rapidly up to the snap-locks due to thebowing effect and then more gradually moving towards the wood stop atwhich point the rods are at their maximum distance apart. This maximumdistance is kept as small as possible while providing some room for thedeflection of the blade guard between the rods.

When not in its locked position, the limit rod is free to pivot betweenan upright position of a little over 90 degrees, as shown in FIG. 14,and a nearly horizontal position, as shown in FIG. 15. This allows theuser to pivot the limit rod up and out of the way to gain better accessto the blade or saw without having to remove the limit rod from theblade guard. Rubber bumpers 248, shown in FIGS. 4 and 48, at the rear ofthe dust port provide a support for the limit rod to lean against whenin its upright position. If the limit rod were to be pivoted upwardswith enough vigor, or forced back while in its upright position, thedust port may break when the limit rod hits the back bumper due to themechanical advantage arising from the length of the limit rod.Therefore, the bumper is made in such a way that it will support thelimit rod in its upright position under normal conditions but will flexand allow the limit rod to pivot beyond the angle of its normal uprightposition if a significant force were to act on the limit rod. Forexample, in FIG. 37 the bumper is shaped like a narrow cylinder of stiffrubber that is held in place in a cylindrical enclosure 250 positionedacross the rear of the dust port and which extends outwards from thecylindrical enclosure on each end. The stiffness of the rubber and thelength at which the ends extend outward from the enclosure determine howeasily the rods can slip past the bumper. To better secure the rubberbumper in the enclosure, both the rubber bumper and the enclosure aretapered outwards slightly moving towards the center of the enclosure andat the middle there is a narrow section 252 in the rubber bumper of alarger diameter that fits in a corresponding groove 254 in the enclosureat the inner edge of each dust port half. In this way, the rubber bumperis restricted from sideways movement so that it does not fall out of theenclosure.

The blade shroud 24 and the limit rod 198 are both supported by the dustport 26 and the dust port is, in turn, supported by splitter 28 whichmounts in the saw and protrudes up through slot 16 in the table insert18. As shown in FIGS. 15 and 37, splitter 28 is a flat metal piece thatfits in the saw behind the blade and has a curved front 256 with abeveled edge that follows the curve of the blade 14. Four holes 258 atthe base of the splitter are used for mounting the splitter in the saw.The top edge 260 of the splitter has a slight curve that follows thecurvature of the divider wall 120 in the upper shell. Divider wall 120is just above the splitter but does not make contact with the splitterwhen the blade shroud is in a horizontal position. As mentioned earlier,there is a dip 182 at the top of the splitter within which one of thescrews 42 in the upper shell rests to support the upper shell in itshorizontal position. The front and top curves of the splitter meet tomake a rounded corner or tip 262 at the front end of the splitter whichextends forward to a point nearly in line with the middle of the blade.

The dust port 26 mounts to the splitter 28 with two bolts, 264 and 266,which pass through holes positioned along the top of the splitter, onehole 268 towards the middle of the splitter and another hole 270 at therear of the splitter, as shown in FIG. 37. Each bolt passes through aset of tabs or extensions that extend down from the bottom of the dustport on either side of the splitter, straddling the splitter. Bolt 264passes through hole 272 in a short dust port extension 274, shown inFIG. 38, that extends down vertically at the rear of the splitter andthen through the horizontally oriented oval hole 270 in the splitter andfinally through hole 276 in another dust port extension 278, shown inFIG. 39, on the other side of the splitter. Hole 270 is oval to allowsome margin in the position of the holes in the dust port extensions inrelation to the splitter to compensate for variations inherent in themanufacturing of the plastic dust port. Bolt 264 screws into a nut 280which fits within a hexagonal cavity 282, shown in FIGS. 39 and 48,molded on the outside of dust port extension 278 to keep the nut fromturning as the bolt is tightened. This conveniently removes the need fora tool to hold the nut during assembly or adjustment of the dust port.As shown in FIG. 38, a long vertical ridge 284 runs down the side of thedust port and dust port extension 274 near the back edge of the splitterto add strength. Two more short ridges 286, one vertical and one nearlyvertical with a slight forward angle, run down dust port extension 274on the other side of bolt 264. The long and short ridges 284 and 286 aremirrored on the outside of dust port extension 278 on the other side ofthe splitter, as shown in FIG. 39.

A thicker and longer set of dust port extensions 288 and 290, shown inFIGS. 38 and 39, extend down from the front of the dust port at aforward angle and straddle the splitter. The head of a bolt 266 sits ina circular cavity 292 at the bottom of dust port extension 288. On theinner side of dust port extension 288, there is a raised circular area294, shown in FIGS. 37 and 46, that protrudes inward and surrounds ahole 296 through which bolt 266 passes. Bolt 266 then passes through themiddle of a bushing 298 which is made like a cylinder with two smallerdiameter sections 300 surrounding a larger diameter middle section 302,as shown in FIGS. 71-73. After the bushing, bolt 266 passes through awasher 304 and then the circular hole 268 in the splitter. Once past thesplitter, bolt 266 passes through a second washer 304, a second bushing298, and finally a hole 310 through a raised circular area on the insidewall of extension 290. Bolt 266 screws into a nut 312 seated in ahexagonal cavity 314 on the outside of extension 290, as shown in FIG.39. A ridge 316 extends down from a couple of the spoke ridges 192 alongthe outside edges of extension 288 for strength. Ridge 316 is mirroredon the outside of dust port extension 290 on the other side of thesplitter. As shown in FIG. 41, the bottom side edge 318 of dust portextension 290 is cut at a forty-five degree angle that slopes inwardmoving down so that the extension does not interfere with the table whenthe blade and blade guard are tilted to forty-five degrees.

One or both of holes 268 and 270, though which the dust port mounts onthe splitter, may be oversized so that the dust port can rotate or tiltslightly upward or downward. For example, hole 270 may be slightlyoversized or shaped so that the dust port can pivot slightly around hole268. Allowing the dust port to pivot or tilt slightly provides a way toadjust the position of the bottom surface of wood stop 200 on the frontend of limit rod 198 relative to the table top. For example, if it isdesired for the bottom of the wood stop to be a certain distance abovethe table, the dust port can be tilted up or down until the bottom ofthe wood stop is at the desired distance and the dust port can then besecured in position. This is useful to accommodate manufacturingtolerances in the limit rod and dust port when the wood stop must beprecisely positioned.

The configuration described of how the dust port mounts on the splitterprovides a rigid connection between the dust port and splitter. In turn,the rigid connection allows the dust port to support a vacuum hosewithout the weight and position of the hose hindering the movement ofthe blade shroud.

The dust port may also be designed with an extension that allows achoice of one of two hose sizes to connect to the dust port outlet.FIGS. 77 and 78 show a blade guard with a dust port 400 that has anextension 402. The extension forms a dust port outlet 404 that the endof a hose can fit into or, alternatively, a hose of a larger diametercan fit over. Three ring shaped ridges 406 are molded on the insidesurface of, and are concentric to the dust port outlet, as shown inFIGS. 79 and 80, which show the right dust port half 408 without otherstructure. The rings are of decreasing diameter moving inwards so thatat least one ring will match the taper of the inserted hose and create asecure press-fit connection.

Blade guard 20 is also equipped with two sets of anti-kickback pawls, asshown at 320 and 322 in FIG. 48 and other figures. The anti-kickbackpawls are mounted to the splitter in such a way that they are able topivot. As a workpiece is moved forward past the blade, it encounters theanti-kickback pawls which, under normal conditions, pivot up when pushedback to allow the workpiece to slide easily underneath. Theanti-kickback pawls gently ride on top of the workpiece as the workpiecemoves past. Once the workpiece passes the anti-kickback pawls, springswork to pull the anti-kickback pawls forward again to their originalposition. However, in a kickback situation where the blade kicks theworkpiece back toward the user, often with some force, the pawls, undercam action, pinch the workpiece between the table and the sharp pointedtips along the bottom edge of the anti-kickback pawls and the sharp tipsdig into the workpiece to prevent the workpiece from being propelledtoward the front of the blade and the user.

FIGS. 59 through 62 show various views of the right large anti-kickbackpawl 320. The large anti-kickback pawl is made of a metal piece withgenerally flat surfaces spaced apart by an outward bend 324 near the topand an inward bend 326 a short distance below the outward bend so thatthe upper portion of the pawl is parallel to, but at a distance from,the bottom portion of the pawl. Notches are cut out along the curved,lower edge of the pawl to create five sharp, pointed tips 328 that areequally spaced along lines drawn from tip to tip. A chamfer 329, cut atabout 45 degrees along the bottom edge of the pawl, makes the tips 328even sharper. The sharp tips are spaced so that ideally only one tipcontacts the workpiece at a time so the load is not spread out over manytips as this would decrease the tips ability to grab the workpiece. Thesharp tips are cut at an angle such that they do not interfere with aworkpiece as it moves forward enabling the workpiece to slide easilyunder the anti-kickback pawls. The sharp tips are also designed to be atan angle such that if the blade was to catch and propel the workpieceback toward the user, the tips of the anti-kickback pawls can grab intothe workpiece to keep it from moving back. The chamfer 329 is cut alongthe inside surface (closest to the splitter) of the left large pawl andon the outside surface (farthest away from the splitter) of the rightlarge pawl, as seen in FIG. 63, so that as the blade is titled to theleft only the tips of the pawl will remain in contact with the surfaceof the table or workpiece. If the chamfer were on the outside face ofthe left large pawl, or the inside face of the right large pawl, thenthe chamfer would tend to line up with, or lie flat on, the table orworkpiece surface and the pawl would not work as effectively. Both theright and left pawls can be stamped with the same tool before bending ifthe chamfers are as described.

While the large anti-kickback pawls work well for situations where thetop of the blade is at least about half an inch above the surface of theworkpiece, small anti-kickback pawls are included to more effectivelycatch workpieces that are less than about half an inch below the top ofthe blade. FIGS. 64 through 67 show a small anti-kickback pawl 322intended for use on the right side of the splitter. A smallanti-kickback pawl for use on the left side of the splitter would be amirror image of the right-side small anti-kickback pawl. As shown inFIGS. 64 and 65, the small anti-kickback pawl is made of a shorter,flat, curved metal piece that has a small rectangular protrusion 330bent outward at a forward angle from the top edge. Notches are cut alongthe lower edge of the bottom portion to create four sharp, pointed tips332 that are spaced at an increasing distance front to back along linesdrawn from tip to tip. Like the large anti-kickback pawls, a chamfer 329is cut at about 45 degrees along the bottom edge of the pawl to make thetips 328 even sharper. Unlike the large anti-kickback pawls, in theillustrated embodiment the chamfer is cut along the inside edge, closestto the splitter, of both the right and left small pawls, as can be seenin FIG. 63, although the chamfer could be like the chamfer on the largeanti-kickback pawls. The chamfer is cut along the inside of the smallpawls so that the sharp tips are farthest away from the blade and thusare better able to grab the workpiece. If the sharp tips were closer tothe blade they may fall into an area where the kerf of the blade has cutaway the workpiece material and there is no material to grab. The sharptips are spaced so that ideally only one tip contacts the workpiece at atime so the load is not spread out over many tips as this would decreasethe tips ability to grab the workpiece. The sharp tips are angled insuch a way that they do not interfere with a workpiece as it movesforward, but the tips grab a workpiece that is moving back towards thefront of the blade.

The anti-kickback pawls are mounted to the splitter by bolt 266, asshown in FIG. 37. A hole 334 in one of the large anti-kickback pawls 320fits over the outer smaller diameter section 300 of one of the bushings298. A coil spring 336, shown in FIGS. 68 and 69, is placed over theraised circular area 294 on the dust shroud. One end 340 of spring 336is curled and hooks onto the back edge of the large anti-kickback pawlas shown in FIGS. 48 and 70. The other straight end 344 of spring 336tucks under and presses up against the underside 346 of the dust port,as shown in FIG. 48. A pawl stop 348, consisting of a small protrusionextending upwards from the top edge of the large pawl, abuts the edge350 of the bottom of the dust port when the large anti-kickback pawlsare not rotated back, as shown in FIG. 48. Pawl stop 348 stops the largeanti-kickback pawl from pivoting too far forward under the action of thespring so that the spring remains in tension and the sharp tips are heldat an angle effective in grabbing the surface of the workpiece. Thespring is loose enough to allow the anti-kickback pawl to pivot to theback as a workpiece moves forward underneath it, but strong enough topull the anti-kickback pawl forward again once the workpiece clears thepawl.

A hole 352 in one of the small anti-kickback pawls 320 fits over theinner smaller diameter section 300 of bushing 298. A coiled spring 354,shown in FIGS. 74 and 75, is loosely wound around the larger diametermiddle section 302 of each bushing 298. One straight end 356 of spring354 tucks under and presses against the underside 346 of the dust port.The other straight end 362 of spring 354 is pressed back behind thesmall rectangular protrusion 330 in the small anti-kickback pawl, asshown in FIG. 76, where tension holds it in place. A pawl stop, whichconsists of a small peg 370 pressed into a small hole 372 in thesplitter such that it protrudes out on either side of the splitter, asshown in FIGS. 37 and 48, stops the small anti-kickback pawl frompivoting too far forward under the action of the spring so that thespring remains in tension and the sharp tips are held at an effectiveangle to grab the workpiece. Peg 370 is attached to the splitter and thesplitter is securely mounted in the saw in order to make peg 370 strongso it can stop the small pawls from rotating too far towards the user ina kickback situation where the small pawls may dig deep into a workpieceand tend to go over center, or past the pivot point.

The large anti-kickback pawls can be disabled by rotating them upwarduntil a bump 374 along the top edge of the lower portion of theanti-kickback pawl hits a stop on the dust port formed by an outwardextension on one of the pivot joint ridges 376 that is nearly horizontaland slightly above the middle of the dust port, as shown in FIG. 48.Once rotated upward, the anti-kickback pawl can be pressed toward thedust port and guided into a catch 378 that extends out from the dustport and which holds the anti-kickback pawl along the side of the dustport. Catch 378 has a small, vertically oriented, ear-shaped tip 380which is flat on the inside surface against which the anti-kickback pawlpresses. Two support ridges 382, shown in FIG. 39, begin from behind themiddle of the tip and extend down and to the rear of the dust port alongthe side of the dust port. A triangular support beam 384 extends inwardsfrom the rear portion of the inside surface of the tip to meet the beamextending inward from the other dust port half and give support to thecatches. The triangular beam is hollow, shown at 386 in FIG. 50, to keepthe walls about the same thickness as the rest of the dust port. Thishelps to minimize warping distortions that may occur when areas ofdifferent thicknesses cool in the manufacturing of the molded plasticdust port.

A pawl guard 388 shaped like a large triangular structure orientedlengthwise along the length of the dust port, rises above the top of thedust port and straddles catches 378 such that the peak of the triangularstructure is just slightly more forward than the front of the catches,as shown in FIG. 38. The pawl guard is formed by two halves, one on eachdust port half, that align together lengthwise with tongue and grooveedges to help with alignment of the two dust port halves. As shown inFIG. 47, the pawl guard consists of a front surface 390 that runs fromthe front bottom corner of the triangle to the peak, a rear surface 392that runs from the peak to the rear bottom corner of the triangle, andan outward facing side surface 394 that runs along the outside edges ofthe front and rear surfaces and is perpendicular to the front and rearsurfaces. Material is removed from the center area of the pawl guard sothat a large, generally triangular hole runs through the middle of thepawl guard. The purpose of the pawl guard is to provide some protectionto the user of the saw when rotating the large anti-kickback pawls intotheir catches—the guard protects the user from the sharp tips on the endof the anti-kickback pawls. The rear surface of the pawl guard 388 hasflanges 396 that extend out to each side and are positioned so that theyrun along and above the arcs traveled by the sharp tip of each largeanti-kickback pawl as the pawls are rotated into their catches. Theflanges extend out the farthest at the top of the pawl guard andgradually taper inward towards the bottom, as best seen in FIG. 40.Again, to minimize warping distortions that may occur when areas ofdifferent thicknesses cool in the manufacturing of the molded plasticdust port, the front, rear and side surfaces have about the samethickness which leaves a hollow area within the pawl guard as shown at398 in FIG. 50.

FIG. 81 shows blade guard 20 connected to a flexible hose 500, which inturn, is connected to conduit 502 that extends above the saw to provideclearance for workpieces pushed past the blade. In the depictedembodiment, conduit 502 is a bent, rigid metal pipe. The conduit issupported by mounts 503 which attach to the saw or to a rail along theback of an extension table attached to the saw. A second hose 504connects conduit 502 to a dust collection port 506 on the table saw,which in turn can be collected to a vacuum or some other dust collectionsystem.

FIG. 82 is a schematic representation of the blade guard 20 incorporatedinto a dust collection system. One end of a hose 500 is connected to thedust port 26 of the blade guard and the other end is connected to avacuum 504. Alternatively, as shown in FIG. 83, hose 500 may beconnected to a conduit that connects to the vacuum system and to whichone or more other hoses may also be attached. A larger hose connected tosaw 508 may also be connected to the vacuum system along with hose 500through a splitter 510, as shown in FIG. 84.

1. A blade guard for use on a power tool with a blade, the guardcomprising: a shroud configured to at least partially shield the blade,where the shroud has a channel through which dust may travel; asplitter; a dust port fixed to the splitter, where the dust portincludes a channel through which dust may travel; and a joint connectingthe shroud to the dust port, where the joint is configured so that theshroud can move, and where the joint is further configured so that thechannel in the shroud operably connects with the channel in the dustport.
 2. The blade guard of claim 1, where the joint is configured sothat the shroud can pivot up and down a predetermined distance relativeto the dust port while the channel in the shroud remains operablyconnected to the channel in the dust port.
 3. The blade guard of claim2, where the joint is configured so that the shroud can pivot up pastthe predetermined distance to close the channel.
 4. The blade guard ofclaim 1, where the blade has a front, where the joint is rearward of thefront of the blade, and where the channel is configured so that dust atthe front of the blade is directed toward the joint.
 5. The blade guardof claim 1, where the channel has a predetermined nominalcross-sectional area, and where the joint is configured so that thechannel in the shroud operably connects to the channel in the dust portwhile substantially maintaining the predetermined nominalcross-sectional area.
 6. The blade guard of claim 1, where the shroudincludes a side configured to pivot around an axis.
 7. The blade guardof claim 6, where the blade has a front, and where the axis is forwardof the front of the blade.
 8. The blade guard of claim 1, where theshroud includes two sides, each side configured to pivot around an axis.9. The blade guard of claim 1, where the shroud includes an upperportion and a side, where the side is connected to the upper portion ata connection location, where the side is configured to move relative tothe upper portion, where the side has an end opposite the connectionlocation, and where the end of the side opposite the connection locationis configured to contact the splitter as the side moves.
 10. The bladeguard of claim 9, where the side moves by pivoting relative to the upperportion around an axis.
 11. The blade guard of claim 1, where the bladehas a front, and where the channel in the shroud includes a curvedsurface forward of the front of the blade.
 12. The blade guard of claim1, further comprising a stop to block a workpiece having at least apredetermined thickness from moving into contact with the blade.
 13. Theblade guard of claim 12, where the stop is configured so that it canpivot upward.
 14. The blade guard of claim 1, further comprising atleast one anti-kickback pawl.
 15. The blade guard of claim 13, furthercomprising a hold to maintain the anti-kickback pawl in a disabledposition.
 16. The blade guard of claim 1, further comprising a stop toblock a workpiece having at least a predetermined thickness from movinginto contact with the blade, and at least one anti-kickback pawl.
 17. Adust collection system for use on a power tool with a blade, the systemcomprising: a guard configured to at least partially shield the blade,and further configured so that a workpiece traveling under the guard canmove the guard, and dust collection means for collecting dust generatedby the power tool while allowing the guard to move freely.
 18. A dustcollection system for use on a power tool with a blade, the systemcomprising; a guard portion configured to at least partially shield theblade, and further configured so that a workpiece traveling under theguard portion can move the guard portion, a dust collection channelassociated with the guard portion, where the dust collection channel hasan outlet, and where the dust collection channel is configured tochannel dust generated by the power tool to the outlet, a vacuum, and aconduit connecting the vacuum to the outlet, where the conduit issupported so that it does not hinder the movement of the guard portion.19. The dust collection system of claim 18, where the power toolincludes a splitter and where the conduit is supported by the splitter.20. The dust collection system of claim 19, where the conduit supportedby the splitter is supported so that it does not move when a workpiecemoves the guard portion.